The invention relates to pulverizing or comminution machines and, more particularly, to pulverizing machines which are comprised of a housing, a steel disc-like rotor rotatable within the housing and having peripheral hammers thereon, a pulverant material inlet means, a pulverized material outlet means, and a linear material on the inside of the housing wall to protect the wall against which some of the pulverant is thrown by the hammers on the disc-like rotor.
In operation of machines with which the present invention is concerned, the material to be pulverized is fed into the housing of the machine via the inlet and comes in contact with the rapidly rotating hammers on the disc-like rotor.
The rotation of the disc-like rotor impacts and pulverizes the pulverant material, some of which impacts the housing liner. The material is pulverized by the hammers on the disc-like rotor, some of which hits the housing liner and is withdrawn from the housing when reduced to the desired particle size.
Heretofore, machines of the above-mentioned description have been made of steel members, but steel abrades away rapidly depending on the pulverant material. Substantially any material, at the high speeds of operation of pulverizing machines, will have a strong abrading effect on even the best steel.
In present pulverizing machines, the steel members wear very rapidly necessitating more or less frequent changing of the rotatable disc-like rotor, depending on the material being pulverized. The maintenance effort to remove the rotatable disc-like rotor and liner from the housing is considerable and is also costly. In a machine of this sort, usually the wear rate is greatest on the hammers first, the surface of the disc-like rotor second and the housing liner third.
The wear rates are of such a ratio to each other that it would be desirable to be able to change the hammers in place on the machine rather than removing the disc-like rotor from the machine or to be able to remove all three of the aforementioned machine parts with a minimum of repair expense and time to refurbish.
To give an example of wear rates in hammers, steel hammers usually must be changed every week. An experiment with ceramic hammers prolonged the life of the hammers to about 2 weeks. With the advent of the present invention, the wear life rate for the hammers is extended to 2 months or more. Wear normally associated with these devices usually centers around (1) the face of the hammers, and (2) the surface of the steel disc-like rotor in the regions thereof adjacent the front and radially inward faces of the hammers.
The wear on the surface of the disc-like rotor takes the form of a dish thereby acting as a hindrance to the outward velocity of the particles just before they hit the liner wall. This hindrance has a detrimental effect on the pulverizing action of the machine. Another action on a very minute scale occurs at the liner wall upon impact. If the wall material is resilient, then some of the impact energy is absorbed by the wall rather than used to break up the pulverant. Pulverizing machines according to the prior art have thus been deficient in respect of the rapid abrasion on the surfaces of the disc-like rotor. When the disc-like rotor is comprised entirely of a steel body, the aforementioned surface wear renders the entire disc-like rotor useless, requiring a brand new disc-like rotor for replacement. The present invention eliminates the need to change the disc-like rotor as often and provides the opportunity to refurbish the used disc-like rotor on a more economical basis than heretofore contemplated.
With the foregoing in mind, an object of the present invention is to prolong the useful life of existing pulverizing machines.
Another object of the present invention is to provide a greater pulverizing force by reducing hindrances to particle movement.
Still another object of the present invention is to reduce maintenance time on such machines.
Another object of the invention is to provide replaceable hammers that can be replaced without the removal of the rotatable disc-like rotor.
Still another object of the invention is to reduce the amount of wear on certain regions in such machines.
Still another object of the present invention is to provide a greater pulverizing effect by providing harder surfaces to impact against.